1. Field of the Invention
The present invention relates generally to a fluid mixing and delivery devices. More particularly, the invention concerns an apparatus for the controlled mixing and incremental delivery of two liquids in a manner such that none of the mixture formed remains within the delivery tube of the apparatus at the end of each delivery cycle.
2. Discussion of the Prior Art
There are a number of situations where it is necessary to separately store two liquid components, to intermix the components and then to controllably dispense the mixture formed. One example of such a situation is found in the adhesive arts wherein, a polymer, such as an oligomer is stored in one container and the cross-linking agent, such as a hardener or curing agent is stored in a separate container. A similar situation exists in those instances wherein the mixing of two components prior to their delivery creates a third chemical with a short pot life. In the medical field a like situation arises when separate components are intermixed to controllably form a mixture such as thrombin-fibrinogen which, following the mixing step, is delivered to an active medical site.
Several devices have been suggested in the past for intermixing and then delivering separate liquid components. However, these devices have typically exhibited various drawbacks. For example, devices which have been suggested for the mixing and delivery of fibrin glue during surgery have traditionally exhibited undesirable clogging. In another vein, many of the prior art devices which attempt to mix and then deliver separate low viscosity liquid chemicals fail to achieve the desired mixture ratio of the components. Additionally, many of the prior art mixing and delivery devices tend to be bulky, unwieldy and quite often require the use of two hands to operate the device.
One type of prior art mixing and delivery device is disclosed in U.S. Pat. No. 5,049,135 issued to Davis. This device comprises a medical lavage syringe apparatus which includes a housing having tabs which engage longitudinal followers on irrigation and aspiration plungers for causing the plungers to stay in a particular rotational orientation during their operation. The aspiration plunger includes a latching surface which engages a tab surface when the aspiration plunger is rotated in an inserted position for locking the aspiration plunger in the inserted position. The plungers include stop surfaces which contact tab surfaces for preventing the plungers from leaving their respective cylinders.
Another type of prior art two component syringe delivery system is disclosed in U.S. Pat. No. 4,979,942 issued to Wolf et. al. The Wolf et. al. system permits the simultaneous delivery of two reactive fluids from a pair of syringes to a delivery site. In one embodiment of the invention a length of tubing exits one syringe and passes through a cannula exiting from the other syringe, to deliver both fluids, separately, but in a controlled volume and space to the delivery site. Alternately, the fluids can mix within the cannula, but its configuration prevents clogging at the delivery site.
The prior art patent to Miller et al, U.S. Pat. No. 4,874,368 discloses a fibrin glue delivery system which comprises a pair of syringe tubes that can be actuated by plungers simultaneously or independently, a connecting member which holds the syringe tubes in parallel alignment and a needle assembly which ensures the components in the syringe bodies will not be commingled until they reach the treatment site.
The present invention seeks to overcome many of the drawbacks of the prior art, two component syringe delivery systems by providing an elegantly simple apparatus which can accurately dispense discrete amounts of two controllably intermixed components. More particularly, the apparatus of the inventions is uniquely designed to automatically clear the delivery tube of the device of any mixture at the completion of each delivery cycle. Accordingly, unlike many of the prior art devices, when the apparatus of the present invention is used to dispense adhesives and surgical glues, the delivery tube of the device never becomes clogged.